Mexican authorities have blamed feuding cartels for similar killings in other parts of the country. But Thursday marked the first time authorities had found such a large number of bodies in San Luis Potosi, Gonzalez said.

More than 47,500 people have died in drug-related violence in Mexico since December 2006, when Mexican President Felipe Calderon announced plans to deploy troops in efforts to combat cartels.

According to Mexico's National Human Rights Commission, more than 5,300 people have disappeared throughout the country in that same time period, and the bodies of 9,000 dead have not been identified.

Officials fear the total number of missing could be far higher, because many disappearances go unreported.

Violence surged in some parts of San Luis Potosi in 2010, as turf battles increased between Mexico's Gulf cartel and the Zetas.

The Zetas started with deserters from Mexican special forces, who quickly gained a reputation for ruthless violence as hired assassins for the Gulf cartel. The partnership between the two criminal groups ended in 2010.